Incidence of gestational hypertension in the Calgary Health Region from 1995 to 2004

BACKGROUND: Hypertension is one of the most common medical conditions complicating pregnancy, and is a major contributor to maternal, fetal and neonatal morbidity and mortality in Canada. OBJECTIVES: To determine the incidence and trends of gestational hypertension among pregnant women in the Calgary Health Region of Alberta. Methods: Gestational hypertension was classified according to current published Canadian guidelines: without proteinuria and with proteinuria. Hospital discharge abstracts were used to identify women diagnosed with gestational hypertension in the Calgary Health Region between January 1995 and December 2004. The Birth Registry of Vital Statistics was used to determine the number of live births and stillbirths in the Calgary Health Region during the study period. Incidence was calculated with 95% CIs. Age-standardized gestational hypertension rates were calculated using 2004 live births and stillbirths as the reference. RESULTS: Over the 10-year period, the incidence of nonproteinuric gestational hypertension was relatively stable even after age adjustment, with an average incidence of 6.3% (95% CI 6.1% to 6.4%). When gestational hypertension was stratified by age, women aged 35 years or older had an almost twofold higher incidence of both nonproteinuric and proteinuric gestational hypertension than those younger than 35 years of age. CONCLUSIONS: Interventions to prevent and improve the management of gestational hypertension, particularly among women aged 35 years and older, are required.